Field
Allyl-cyanoacrylate-containing compositions with an anhydride aromatic component, which when cured confers improved moisture resistance, are provided.
Brief Description of Related Technology
Cyanoacrylate adhesive compositions are well known, and widely used as quick setting, instant adhesives with a wide variety of uses. See H. V. Coover, D. W. Dreifus and J. T. O'Connor, “Cyanoacrylate Adhesives” in Handbook of Adhesives, 27, 463-77, I. Skeist, ed., Van Nostrand Reinhold, New York, 3rd ed. (1990). See also G. H. Millet, “Cyanoacrylate Adhesives” in Structural Adhesives Chemistry and Technology, S. R. Hartshorn, ed., Plenun Press, New York, p. 249-307 (1986).
In the industrial marketplace, the moisture durability of cured cyanoacrylate adhesives could stand improvement. Indeed, the poor moisture durability is a feature for tissue adhesives based on cyanoacrylates (such as those sold under the INDERMIL tradename), as such tissue adhesives tend to sluff off after washing with warm water.
The lack of moisture durability is particularly apparent on metal substrates, which is a problem for industrial uses. Cured cyanoacrylate adhesives are susceptible to hydrolysis when exposed to moisture, resulting in a rapid reduction in the molecular weight of the cured cyanoacrylate. As a result, bond strength is compromised.
In the past, efforts have been made to improve the durability of cured cyanoacrylate compositions, with a particular focus on exposure to elevated temperatures.
For instance, U.S. Pat. No. 3,832,334 is directed to the addition of maleic anhydride, which is reported to produce cyanoacrylate adhesives having increased thermal resistance (when cured) while preserving fast cure speed.
U.S. Pat. No. 4,196,271 is directed to tri-, tetra- and higher carboxylic acids or their anhydrides, which are reported to be useful for improving heat resistance of cured cyanoacrylate adhesives.
U.S. Pat. No. 4,450,265 is directed to the use of phthalic anhydride to improve heat resistance of cyanoacrylate adhesives. More specifically, the '265 patent is directed to and claims an adhesive composition comprising a polymerizable constituent the major part of which comprises at least one ester of 2-cyanoacrylic acid, characterized in that the composition additionally comprises a proportion of phthalic anhydride effective for favorably influencing the strength and/or durability of adhesive bonds formed from the composition, under exposure to moisture or elevated temperature. The effective amount is reported as 0.1% to 5.0%, such as 0.3% to 0.7%, by weight of the composition. The '265 patent reports the superiority of phthalic anhydride over compositions where no additive was used, and where maleic anhydride was used (though less pronounced in the case of stainless steel lapshears than in those of aluminium).
U.S. Pat. No. 4,532,293 is directed to the use of benzephenonetetracarboxylic acid or its anhydride to provide superior heat resistance for cyanoacrylate adhesives.
U.S. Pat. No. 4,490,515 is directed to cyanoacrylate compositions containing certain maleimide or nadimide compounds to improve hot strength properties.
Allyl-cyanoacrylate is known to undergo a cross-linking reaction through the allyl functional groups, once given a post-bake (either as an additional process step or as a result of the environment in which they are used) after initial cure occurs. This provides improved thermal stability.
Despite these efforts, there has been a long standing, but unmet, desire to achieve more robust performance from cyanoacrylate compositions, particularly under elevated relative humidity conditions. It would accordingly be quite advantageous to provide a solution to that desire.